Many radio and wireline transmitters use the power back-off (PBO) technique in order to reduce the distortion caused by the intermodulation terms generated by the power amplifier(s) of the transmitter. This distortion can act as a bottleneck for the signal-to-noise ratio (SNR) on the transmission side, especially if the energy spectrum of transmitted signal is not totally flat, for instance due to electro-magnetic compatibility (EMC) regulations. Additionally, when the spectrum of the transmitted signal is not flat, the power back-off can be used in order to reduce the dynamic range of the signal. This procedure can help to improve the SNR value on the receiver side, if the signal is processed by components having quantification noise. Therefore, the power back-off on transmission can be used to increase the maximum SNR value that the transmitter-receiver (TX-RX) system can grant to the frequency bands with lower energy.
On the other hand, the power back-off technique can reduce the maximum SNR value that the TX-RX system grants to the frequency bands with higher energy. These maximum SNRs value are only limiting if the channel SNR values are higher than these maximum SNR values for each carrier frequency. Otherwise, these maximum SNR values are not behaving as bottlenecks. Currently, wireline communications such as power-line communication (PLC) either do not use PBO or make a limited use of PBO where the applied PBO is independent of the channel noise.